Traditional personal listening devices utilize one or more drivers as audio reproduction sources. The sound waves from these drivers are commonly carried from an enclosed, sub-miniature electro-acoustic transducer or driver, through a tube or sound bore connected thereto, and terminating at the tip of the canal portion of the device. In such earphones, the device's overall frequency response is affected by the length and inner diameter of the tubing or bores used to direct the output of the drivers to the earpiece or tip of the device. This use of tubing or bores is used to tailor the audio response of the drivers, but also introduces tube resonance, affecting the frequency response of the driver connected to the tubing or bore. Tubing or bores can also constrict the sound waves passed from the driver through the tube or bore, often complicating the acoustic design of the device or exerting a deleterious effect on the overall fidelity of the system.
Alternate arrangements of transducers and other components in earphones can simplify the design or construction of the device, or improve its sound-reproduction fidelity. These benefits may be of significant value in this field.